Ok…so….I’ve been reading a little about the “Hot Big Bang Theory” and it mentions that at the moment before the “bang” the singularity was infinitely hot but 1 second after the bang the universe had cooled to something like 10 thousand million degrees and now is in most regions a couple of degrees above absolute zero (I think that’s about –275 degrees… anyone?) This got me thinking….what is the coldest temperature possible? Is there anything colder than the cooling universe? Is “cold” just the absence of “heat?”
They call it absolute zero for a reason. Molecular motion stands still at about -273 degrees celsius. Can’t get colder than that.
OR…
0° Kelvin
OR …
~-459° Farenheit
It should be noted that Absolute Zero is impossible to reach. You can get arbitrarily close to it but you’ll never quite get there.
Deepest outer space (i.e. as far from any star or planet as you are able to get) is about 3[sup]o[/sup] above absolute zero.
Scientists have been able to do a lot better here on earth and have cooled atoms down to 0.000000001 (a few billionths of a degree) above absolute zero. When they did this they saw a starnge and rare creature called a Bose-Einstein Condensate form. Essentially the atom they cooled ‘smeared’ out in space to much larger than its normal size. It did this to keep within the Heisenberg Uncertainty Principle (that you cannot know both the position and velocity of a particle with perfect accuracy…the better you know one detail [of the two] the less accurate you are about the other detail. By slowing an atom down to very close to absolute zero you know the velocity of the atom with great precision. One would think you would then also know the location (barely moving at the bottom of your detector). The Universe is hip to this trick though and smears out the particle such that its position is not known well at all.
Absolute Zero is impossible to reach currently, but who knows what we will be able to do? Absolute Zero is the coldest temperature possible, we just can’t do it yet.
Absoluite zero is impossible to reach theoritically in thjermodynamics, that said given the statisical nature of thermodynamics, it could just be possible with a lot of luck.
:smack:
Ok got it! Thank you all for the clarification. So here’s another related question. What would happen if absolute zero could be reached somehow.? Are there any calculations for this possibility? Theories? Would everything cease to exist? I’m getting sci fi here and thinking of Vonnegut’s Ice-9 in the “Cat’s Cradle”
Ok so in “our” universe or absolute zero would have to be unattainable for our universe to be able to support the laws that exist in it but are there any notions that in another universe those particular laws do not exist so that absolute zero could be reached?
Using my “beer in a bucket of ice” theory…you need ice at 32 degrees to chill down a beverage but you won’t chill it beyound 32 degrees. Wouldn’t you need something colder then absolute zero to cool something to absolute zero.
Pardon my puney brain thinkin’.
Not that puny, since it’s absolutely correct. Energy wants to move from a source to a sink. You can’t create cold, though you can move heat from one place to another. In order to move heat, you need something cold to warm up.
One’s nipples would become hard enough to cut diamond.
It’s true. I saw it on Nova.
The laws of thermodynamics are some of the strongest laws in physics they hold in just about every situation (though as I said before given their statistical nature there’s always a minucle possibilty they won’t, especially on very small scales). If absolute zeroes reach, nothing magical happens (well except the odd Bose-Einstein condensate) and particles still have vibrational energy (so-called zero-point energy).
That makes sense on the face of it but remember that temperature is an indicator of motion. To go cold all you want to do is slow down the object (or atoms in that object) that you are trying to cool. In the case fo the guys who got to within a few billionths of a degree of absolute zero they did it with lasers. Lasers ringed the chamber containing the atom they wanted to cool down. If the atom moved one way a laser would fire and push back. Then anopther laser would fire nudging against its motion. Think of stopping a thether ball by poking in opposite directions to its motion with your finger till it stopped and you kinda have the idea.
Unfortunately I think you’ll run into issues as the thing gets slower and slower. There are limits (maybe Planck?) to just how small a measurment you can take. Eventually you’ll be unable to distinguish which way the particle is moving to counteract its motion. This will be exceedingly cold and slow but still not absolute zero.
But what if it’s absolute zero… and the wind was blowing? How cold would it feel?
The motion of the wind would raise the temperature, so it would feel slightly warmer. 
But you’d still wish you had your mittens.
Nitpick: It’s not 0° Kelvin, it’s simply zero Kelvin, or 0 K. Kelvin is the name of the SI unit of temperature.
Who cares about nipples! Think about the shrinkage!
At absolute zero there would be no wind, because even hydrogen would be frozen.
Nothing especially spectacular (I think). Unless you’d get a Bose-Einstein Condensate the size of the Universe. Frankly it’ll take Chronos and company to answer that one.
WAG:
At Absolute Zero a particle might conceivably grow over time. Since the velocity is known with 100% precision I suppose the position would need to be known with a 100% lack of precision. Thus the probability function that represented the particle’s position would grow ever larger to include all possible points the particle might theoretically make it to within that timespan. Of course you could collapse the whole thing as soon as energy was added back to the particle to raise it back above 0 Kelvin. That wouldn’t take long as there is lots of energy available in the universe. The guys who got to a billionth of a degree above 0 K had to isolate the equipment from vibrations that came from a highway over a mile away. Supposedly walking in the room with the equipment (vibrations again) would affect the temperature. Doesn’t seem like it would take much to get the BEC back up in temp. This also suggestes that even if MC Master of Ceremonies is correct that staistically a particle might drop to 0 K it will likely not stay there for long at all (a really, really short span of time I would guess).
Don’t think “beer in a bucket of ice”, then. Here’s a couple of ways to lower temperature without having something colder than the temperature you want to reach:
Take an insulated bucket of crushed ice and stir lots of salt in it. The ice melts, 'cos the freezing point of salt water is lower than the freezing point of fresh, but to turn liquid it has to reassign some of the heat energy that’s in it… This is slightly complex, but when something is liquid a certain amount of the heat in it isn’t expressed as “temperature” but just as “energy keeping this thing liquid”. Latent heat of fusion, is the technical term. So the amount of heat in the insulated bucket stays constant, but some of it has turned into latent heat of fusion, and there’s less left over to keep up the temperature - so the temperature drops. You can get all the way to 0 degrees Fahrenheit this way, and this is exactly how Fahrenheit arrived at the zero point for his scale.
Take some air and compress it in a pump. It gets warmer. Allow it to cool back to room temperature. Now allow it to expand. It gets cooler - cooler than you started with. This is how your fridge works. An extension of this technique will let you create liquid air.
And if this isn’t an occasion to use the 
smilie, when is?